Abstract
Adding fibers is highly effective to enhance the deflection and ductility of fiber-reinforced polymer (FRP)-reinforced beams. In this study, the stress and strain conditions of FRP-reinforced lightweight aggregate concrete (LWC) beams with and without fibers at ultimate load level were specified. Based on the sectional analyses, alternative equations to predict the balanced reinforcement ratio and flexural capacity for beams failed by balanced failure and concrete crushing were established. A rational equation for estimating the short-term stiffness of FRP–LWC beams at service-load levels was suggested based on Zhu’s model. In addition, the contribution of the steel fibers on the short-term stiffness was quantified incorporating the effects of FRP reinforcement ratio. The proposed short-term stiffness model was validated with measured deflections from an experimental database for fiber-reinforced normal weight concrete (FNWC) beams reinforced with FRP bars. Furthermore, six glass fiber-reinforced polymer (GFRP)-reinforced LWC beams with and without steel fibers were tested under four-point bending. Based on the test results, the proposed models and procedures according to current design codes ACI 440.1R, ISIS-M03, GB 50608, and CSA S806 were linked together by comparing their predictions. The results showed that increasing the reinforcement ratio and adding steel fibers decreased the strain of the FRP bars. The flexural capacity of the LWC beams with and without steel fibers was generally underestimated by the design codes, while the proposed model provided accurate ultimate moment predictions. Moreover, the proposed short-term stiffness model yielded reasonable estimations of deflection for both steel fiber-reinforced lightweight aggregate concrete (SFLWC) and FNWC beams.
Highlights
This paper aims to establish the balanced reinforcement ratio, ultimate moment and deflection equations of lightweight aggregate concrete (LWC) beams with and without fibers
In order to evaluate the accuracy of the short-term stiffness model proposed, the measured and predicted deflections under service load levels (Ms ) of fiber-reinforced normal weight concrete (FNWC) beams reinforced with fiber-reinforced polymer (FRP) bars tested in the literature are compared in Table 1 and Figure 4
The reinforcement strain of beam SLC–0.92 is not presented since the strain gauges wereshows broken strains in the tensile FRP bars and the compressive concrete against the applied moment of the
Summary
With the urgency of the sustainable infrastructure development and the innovation of structural system, fiber-reinforced polymer (FRP). Bar has become increasingly applied in engineering construction as a substitute to conventional steel reinforcement, due to its lightweight, high tensile strength and non-corrosive properties [1,2,3,4,5]. The reduced mass of lightweight aggregate concrete (LWC) allows for a reduction in cross section and reinforcement amount in the concrete structural members, and exerts a favorable effect on both seismic resistance and economy [7]. In view of the characteristics of FRP and fiber-reinforced lightweight aggregate concrete (FLWC), their combined use could be beneficial in improving the strength-to-weight ratio, and in decreasing the overall life cost of the structures [8].
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